In a typical wireless communication system such as a cellular radio frequency (RF) radiotelephone system, a radio subsystem including a base station system having a controller and a plurality of transmitters and receivers is in communication with a switching center. An interworking unit is often in communication with one or more elements of the radio subsystem. The radio subsystem is responsive to a mobile communication unit, or station, operating within an area served by the base station system.
Multiple access wireless communication between the radio subsystem and the mobile station occurs via RF channels which provide physical paths over which digital communication signals such as voice and data are transmitted. A wireless communication system using code division multiple access (CDMA) channelization is described in detail in standards promulgated by the Electronics Industries Association (EIA) and the Telecommunications Industry Association (TIA), such as TIA/EIA Interim Standard 95 (IS-95), IS-95A and IS-96, each such standard incorporated herein by reference.
To facilitate the wireless transfer of a data communication, many mobile stations are capable of receiving or transmitting digital data from/to computers, facsimile machines and other data sources.
FIG. 1 illustrates a typical call setup procedure for a data communication, such as a facsimile communication, in code division multiple access (CDMA) system. First, a mobile station 44 sends a request for a data communication 10 to a radio subsystem 46. Request 10 may be made via an air interface protocol such as IS-95. Radio subsystem 46 then requests a data circuit 12 in an interworking unit 56, which may include one or more modems (not shown). Request 12 may be implemented using IS-687 protocol, providing for the setting up and tearing down of a data circuit between a radio subsystem and an interworking unit in a cellular communication system.
Next, mobile station 44 and interworking unit 56 exchange commands and data to establish a first data channel 16 (i.e., a mobile station path or data circuit) such as a communication protocol stack. A suitable stack may be established using IS-99 protocol, for example. It is then possible for mobile station 44 and interworking unit 56 to exchange commands and responses 18 to configure a modem (not shown) associated with interworking unit 56 based on the requirements of mobile station 44. One or more commands and responses 18 may be performed to properly configure the modem. Examples of commands and responses 18 include, but are not limited to, baud rate instructions and carrier detect timeout instructions and other commands and responses as defined in IS-99, incorporated herein by reference.
At this point, it is generally necessary to establish a second data channel 22, such as a PSTN data circuit, to provide connection from mobile station 44 to a called device (not shown) such as a landline facsimile machine or computer. Steps involved in establishing a PSTN data circuit are well-known, and may include but are not limited to: establishing a landline data circuit between the radio subsystem and/or modem and the PSTN; dialing a number associated with the called device; and waiting for the called device to answer. In addition, prior to initiation of data communication 30, modem negotiation 26 may be performed according to well-known methods.
To indicate that second data channel 22 has been established and modem negotiation is complete, a message, such as connect message 28, is directed to mobile station 44 via the first data channel. Once connect message 28 has been received by mobile station 44, data communication 30 may commence.
It can be seen that the traditional manner of transmitting data communication 30 suffer from various problems. For example, valuable RF resources may be usurped by waiting for the establishment of second data channel 22 while no data transfer is being accomplished by mobile station 44, and the total time required to transmit data communication 30 may be increased.
There is therefore a need for a method and system for transmitting a data communication from a communication unit such as a mobile station associated with a wireless communication system to a called communication unit which minimizes an amount of time needed to complete the data communication.